My HP Photosmart C4780 does not print or scan. When I try to copy a document I get a print out of colorful vertical lines. When I scan a document I get the same result, the document is a picture of colorful vertical lines. However, my printer prints out documents just fine.

Just two guesses: you have a memory card in the printer, or you connected the USB cable when first setting up before prompted to do so, and now have to disconnect everything and start over, including installing the driver software.

I should also add that it use to copy/scan just fine and then suddenly started having this issue. I had made no major updates or changes when it started having issues. When I first set it up I plugeed in the cable when prompted and there is no memory card in the printer. I will try to reinstall the printer to see if that fixes it, let me know if anyone has any other suggestions.